Moving indication storage tube apparatus



Oct. 18, 1960 M. J. TAUBENsLAG Erm. 2,957,105

MOVING INDICATION STORGETUBE APPARATUS Filed Feb. 13. 1958 Unite Safes Patent C) MOVING INDICATION STORAGE TUBE APPARATUS Morris J. Taubenslag, Baltimore, and David E. Goulden, Arundel Hills, Md., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Feb. 1s, 195s, ser. No. 715,039

6 claims. (C1. 315-12) This invention relates to improvements in moving indication cathode ray apparatus employing a direct viewing storage tube, and more particularly to such apparatus in which the brightness of the visual indication is automatically maintained at a desired value despite variations in the rate of movement of the indication across the screen of the tube, to thereby eliminate blurring, blooming, and other undesirable effects in the indication.

The apparatus is particularly Well adapted for sirnultaneously presenting or displaying on a single screen a plurality of symbols or other indications of different desired persistences.

Apparatus for writing multiple indications on a stor- -a-ge tube screen where different persistences of the indications and their information are required are used in a number of different applications. This mode of operation of storage tubes is desirable, for example, Where radar information which is displayed for a long period of time is simultaneously displayed with tactical symbols which move across the tube face at varying rates.

As is well known in the art, all storage tubes have a controllable erase rate, erasing being accomplished usually by an erase beam moving ahead of the Writing beam, or by an erase potential applied to the mesh support for the storage dielectric material. In the latter case .the erase rate is substantially uniform throughout the surface of the insulator or dielectric material of the storage tube, and therefore the problem of controlling the storage and brightness of multiple varying symbols or indications has not easily -been resolved. Prior art attempts have been made utilizing control of the potentials of the storage tube writing gun for symbol display at iirst and second cross-over points on the characteristic curve of secondary emission versus primary-electron energy, so that secondary emission from the insulator is minimized. However, considerable `difficulty arises from attempting to operate a storage tube at one of these cross-over potentials, including the following: the insulator non-uniformity causes a crossover potential which varies at different points on the insulator; since the lirst crossover point is at a low potential, the Writing beam has a low velocity and therefore does not develop a bright or well focused trace, and is affected by stray magnetic fields; the second crossover point is at an eX- tremely high potential and therefore is not attractive operationally; both crossover points usually lhave' extremely critical control voltage levels, and therefore extreme regulation of supply or a closed loop type of control isV necessary. Because of the above-mentioned diiculties, systems attempting to write through at crossover have not proved satisfactory.

The `apparatus of the instant invention overcomes these and other disadvantages of the prior art, and utilizes a unique method of displaying symbols and other yindin 2,957,105 Patented Oct. 18, 196i) 2 face of the storage tube `and the amount o f `charge thereon, with the result that the number of electrons from the flood gun striking the phosphorescent screen is `reg= ulated and the brightness of thevisual indicationon face of ythe tube is automatically maintained at the correct value.

Accordingly, a primary object o f the` instant invention is to provide new and improved moving" indication storage tube apparatus.

Another object of the invention is .to provide new and improved multiple indicationY apparatusemploying storage tubes.

A furthe'r'object of the invention is to provide a new and improved circuit in'which the ywriting'beam intensity and therefore theV amount of storage controlling the passage of flood gun electrons'whch provide a'fvisual indication of a direct viewing storage tube is automatically controlled' by "the 'rate-of-'clange' of position kof the indication.' 'Y

Other `objects and advantages will become apparent after a studyl of the `following specification when v4read in connection with' the accompanying drawng,'in which: Figure 1 is a schematic electrical circuit diagram of the preferred embodiment of they invention; Fig. 2A is a View of the storage t'ube'screen' accordin'g'to one' use of the invention; and Fig. 2B' is' a series 'of graphs illustrating the operation of the apparatus of Fig'. l.' 'T

In Figure' 1, to which particularattention is directed, the reference numeral'10designatesacathode ray storage tube, it being understood that 'the storage tube may have any suitable dimensions.' *As' will b'e readily understood by those skilled' inthe art, storage tubes of the electrical input-visual 'out-put' typeA may comprise 'generally -a foraminated 4dielectric element at one 'end of the ytube located adjacent a phosphor element constructed and arranged to provide 'an indication in themvisual spectrum when bombarded by electrons, A reading or ood kgun iloods the entire vStorage `dielectric grid with a collim-ated beam of relatively llow energy electrons some of which may `pass to the phosphor element; la writing `gun provides 4a moving beamwwhich, moving across the dielectric, varies the charge thereon by causing secondary emission from the dielectric, vand variations in the charge on the'die'lectric permit passage. of 'Varying numbersl of electrons tothe phosphor viewing screen, which is maintained at a high positive potential. 'Accordingly, there is produced on the viewingscreen' Aa visual image of the charged reas on thestorafge'grid assembly'.

The storage tube l0 is of the type having twoelectron guns with their'sources of .electron emission, these being the cathodes 1l and 12, the`cathode 11 being part of the ood or reading gun, and the cathode lltbe'in'g' part of the writing gun.' The cathode ll'may be connected vby lead 13 to ground 14.l An electron acceler'ating'for focusing anode'l is shown disposed in predetermined spaced position to thecathode 11, the accelerating anode l5 being connected by'lead v115 to the positive'y terminal of a suitable Vsource of potential 17 `having ythe 'other terminal thereof connected to ground 1:4. The source of potential 17 maybe of the order o f 200 voltsf The cathodell is designed'to emita flood of electrons .which are generally focused and' accelerated outward by `the cylindrical kanode focusing member 15, and are' then collimated into parallel paths'by the cylindrical collimating element'lS, which may if desired .be' la'conductive coating on the inside Vwall of the tube, and' which is connected by lead 19 .to one terminal of a suitable Vsource of potential l2t) which yhas the' other .terminal thereof connected to rground `14. ',The'collimating'electhe source of potential 20 being, for example, of the order of l volt to 150 volts.

At the display end of the tube, that is, the right-hand end as viewed in the figure, the inside face of the tube may have thereon a layer of transparent conducting material, having adjacent thereto a layer of a substance suitable for providing a visual indication, while bombarded by electrons, for example, a phosphor compound, these being both designated by the reference numeral 21, and the layer of transparent conducting material has applied thereto by lead 22 a positive potential obtained from source 23 of, for example, 5 to l0 kilovolts, the negative terminal of source 23 being connected to ground 14. It should be understood that these and all other voltages stated herein are typical for one general type of tube in -accordance with other voltages applied thereto, are given merely for purposes of illustration, and may be varied if desired.

There are disposed near the right-hand end of the tube as viewed in the figure, two meshed elements or screens spaced predetermined distances from each other. The spacing is shown in the gure in a somewhat exaggerated degree for clarity of illustration, it being understood that the two mesh or screen elements hereinafter to be described may be spaced somewhat closer than shown. Nearest the aforementioned coated surface 21 is a storage dielectric element, this being generally designated by the reference numeral 24. This storage element 24 may be conveniently formed by spraying a suitable dielectric material on one side of a suitable metallic mesh, shaped to t inside the tube 10. `In the figure, the dielectric material is shown at 25 whereas the metallic mesh portion of the element 24 is designated 26. A number of dielectrics are suitable for use in storage tubes; for example, the dielectric material 25 may be a silicon monoxide. The metallic mesh portion 26 is connected by lead 27, resistor 28, and source of potential 34 to `ground 14. Source of potential 34 may be of the order of volts, and has the positive terminal thereof connected to resistor 28. Lead 27 is also connected by way of capacitor 29 to a suitable erase pulse generator 30 which may be of any convenient design for generating positive erase pulses for application to the storage element 24, and which is provided for reasons which will become hereinafter more clearly apparent. Erase pulse generator 30 is also connected to ground 14, and has controls 81, 82, and 83 for varying the erase pulse amplitude, width, and repetition rate, respectively.

The operation of the erase pulse generator 30 will be readily understood by those skilled in the art and need not be described in detail. The application of the positive erase pulse to lead 27 provides that some erasing effect is applied over the entire insulator surface of dielectric 25. Uncharged or low charged portions may be momentarily brought back to substantially equilibrium floating potential, which floating potential controls the background brightness of the display tube. Sufce it to state, the electron beam of the writing gun, hereinafter to be described, varies the charge on the storage dielectric 25 by causing secondary emission, and a positive charge is created in the dielectric. The trailing edge of the erase pulse is negative going, and by capacitive action induces a negative charge on the face of the dielectric material 25, thereby erasing at least partially the positive charges of the writing process.

A second metallic screen 31 is provided, mounted as shown and disposed a predetermined small space from the aforementioned dielectric 25. Screen 31 serves as a collector electrode for secondary emission electrons from dielectric 25, and is maintained at a low positive potential with respect thereto. Screen 31 is accordingly connected by way of lead 32 to the positive terminal of a suitable source of potential 33 having the otheror negative terminal thereof connected to ground 14. Source of potential 33 may be of the order of 150 volts.

The aforementioned cathode 11 and the accelerating or scattering electrode or anode 15 provide, as aforementioned, a ood of electrons which may generally follow the paths indicated by the reference numeral 37, and it is noted that the element 15 disperses the electron stream from cathode 11 and that the collimating electrode 18 forms these electron paths into paths which strike the insulator 25 at a substantially perpendicular angle, after passing through the mesh of collector 31. Some of the ood electrons as aforementioned may pass through element 24 and reach viewing screen element 21.

The aforementioned cathode 12 is constructed and arranged to provide the writing beam of electrons, and is connected by way of lead 9 and a suitable source of potential 38 to ground 14. The source of potential 38 may be of the order of 2000 volts, and has the negative terminal thereof connected to lead 9. lIt is desirable to bias cathode 12 near cutoff so that a writing beam occurs only when a positive gate pulse is applied to grid element 39, and accordingly grid 39 is made negative with respect to ground as will be seen hereinafter.

Disposed in proximity to the aforementioned cathode 12 is the aforementioned intensity control grid 39. Control grid 39 is connected by way of lead 70, resistor 71, and lead 73 to the arm 78 of a potentiometer 77 which is connected across a small portion of the negative end of battery or source of potential 74. Source of potential 74 may be of the order of 2015 volts, and has the positive terminal thereof connected to ground 14. Disposed adjacent grid 39 is a second grid 35 connected by lead 36 and source of potential 72 to ground 14. Source of potential 72 may be of the order of 1000 volts, and has the negative terminal thereof connected to lead 36.

Disposed in proximity to grid 35 are two sets of deection plates, the vertical deection plates being designated 40 and 41, and the horizontal deflection plates being designated 42 and 43. The deflection plates 40 and 43 are connected by way of lead 44 to ground 14. Vertical deection plate 41 is connected by way of lead 45 to a vertical deection amplifier shown in block form and generally designated 46. The aforementioned horizontal deection plate 42 is connected by way of lead 47 to a horizontal deflection amplifier shown in block form and generally designated 48. The pairs of deflection plates 40 and 41, and 42 and 43, when energized in conventional manners to set up an electrostatic eld, provide for movement of the writing beam of electrons 75 from cathode 12 to various areas of the dielectric 25, in the usual manner of a writing gun, which will be readily understood by those skilled in the art.

The operation of storage tubes has been extensively described in the literature of the art and need not be described herein in great detail. A discussion of the basic theory of cathode ray tube storage may be found, if desired, in a book entitled, High Speed Computing Devices, by McGraw-I-lill Book Company, 1950, pages 354- 374 inclusive, and in Storage Tubes and Their Basic Principles, by Knoll and Kazan, John Wiley and Sons, 1952. Su'ice it to say here, that electrons striking the aforementioned phosphorescent surface or material 21 cause luminescence at the point where they strike, and that the luminescence or brightness of a given point or small area may be controlled by varying the charge on the adjacent area of the dielectric 25. In accordance with the secondary emission characteristic of dielectrics, the charge on the dielectric 25 may vary at the point or area where the writing beam of electrons 75 impinges thereon, which may accordingly result in variations in the number of electrons striking the luminescent surface.

The apparatus of the instant invention is adapted, as forementioned, for use in radar apparatus where certain symbols or indications displayed on the cathode ray tube preferably persist for a relatively long time, while other symbols or indications preferably persist for a relatively short time and may move rapidly across the face or viewing screen of the tube. If a symbol is to move rapidly across the face of the tube, the brightness and persistence of the symbol at any one spot on the tube must not be too great or there would be a blurring eiect, or possibly saturation and blooming, or a multiple symbol presentation which would result in confusion or inaccuracy. The persistence of a luminescent or visual indication is, as is well known in the art, at least to some extent proportional to the number of electrons striking the phosphor surface. The apparatus of the instant invention is constructed and arranged to provide for automatic control of the brightness of the indication in accordance with variations in the rate of movement of the indication across the face or screen of the tube, to thereby provide for a moving :symbol or indication in which blurring and other undesirable eifects are eliminated. The heart of the invention is the automatic control of the writing beam intensity in accordance with the rate-of-change of position of the writing beam.

The symbol or other indication is usually formed by a small alternating current voltage or pulsed voltage of predetermined wave form which is superimposed on a large direct current voltage which positions the beam in one plane or dimension on the face or screen of the tube, such for example as illustrated by the wave form 49 of the signal applied on lead 5t) to the aforementioned horizontal deflection amplifier 48. The signal on lead Sti may, for example, be obtained from the arm 5l of a potentiometer 52 connected to a terminal 53 which has a composite Wave form including a direct current component applied thereto. In like manner, a direct current voltage having an alternating current voltage superimposed thereon, such, for example, as the wave form 54 may be applied by way of lead 55 to the aforementioned Vertical deflection amplier 46, the signal on lead 55 being obtained from the arm 56 of a potentiometer 57 connected to terminal 58 and having applied thereto a signal or voltage similar to the voltage applied to terminal 53.

Automatic control of the Writing beam intensity is provided by a portion of the circuit in which a gate of variable amplitude is generated, having an instant amplitude proportional to the instant rate-of-change of the direct current deliection component of the composite signal. The composite signal 49 on lead 5@ is applied to a filter 59 which eliminates the alternating current component therefrom, while the composite sginal 54 on lead 55 is applied to a filter 6i) which eliminates the alternating current component from the signal 54. The variable direct current outputs of the filters 59 and 6i) are applied to a pair of differentiators 61 and 62, and the outputs of the respective diiferentiators on leads 63 and 64 are voltages or signals substantially proportional to the rates of change of the direct current signals supplied thereto. The signals on leads `63 and 64 are summed at 65 and the combined signal on lead 66 is substantially proportional to the combined rates of movement of the writing beam and the symbol in vertical and horizontal planes or directions. The signal on lead 66 is applied to a gate generator 67 which may be of conventional design and which is constructed and arranged to generate a gate signal, the amplitude of the gate signal being proportional -to the signal applied to the gate generator by way of lead 66 and accordingly proportional to the rate of movement of the indication on the screen. The gate generator 67 provides a small positive gate on lead 63 whilethere is no movement ol the writing beam 75 and no movement of the visual indication. This gate Vis great enough to provide for a visual indication of proper brightness with the writing beam stationary. Control 76 is provided for adjusting the value of this gate. As the writing beam andV indication move, the positive gate increases in value. Control 79 is provided for adjusting the rate of increase. As

'6 aforementioned, preferably the writing gun or cathode is biased `at or slightly beyond cutoff, and a positive pulse must be applied to the lgrid or control element 39Ato secure the Writing beam 7S for deflection by the aforementioned plates 4d, 41, 42 and 43. The positive gate output of gate generator `67 is accordingly applied to lead 68 and thence is coupled by Way of capacitor 69 and lead 70 to the aforementioned intensity control grid 39, lead 70 as aforementioned being connected by way of resistor 71, lead 73, potentiometer 77, and source of potential 74 to ground 14. The gate is applied to the grid 39 of the writing gun of the storage tube 10 in time coincidence with the generated indication or symbol to thereby vary beam current as a function of gate amplitude, which, in turn, isa function of the rate of movement of the symbol or iiidication. Y

As aforementioned, the apparatus is especially suitable for use for multiple symbol or multiple indication display, time sharing being provided for the diiferentiating circuits and deflection circuits. Suitable switching apparatus, not shown, preferably having a controllable'switching rate is provided for alternately applying to the indicating circuits including leads Sil and 55` signals corresponding to symbols or indications which have already been generated in any convenient apparatus', not shown.Y

As an example of the use of the invention for multiple indication display, assume that it is desired to permanently display on the viewing screen a radar indication, for example, a range marker 88, Fig. 2A, which is provided by a radar signal 86, Fig. 2B, graph X which recurs every four seconds, the radar signal itself lasting, for example, one-tenth of a second; and that it is` desired to simultaneously display on the viewing screen a moving tactical symbol or indication 89 provided by a tactical signal 8'7, Fig. 2B, graph Z which lasts, for example, one second and which occurs at the same repetition rate as the recurring radar signal and at a time having definite time relationship to the occurrence of the radar signal, the switching apparatus also being synchronized withv both the radar and tactical symbol signals. The switching apparatus, not shown, may connect `the storage tube apparatus for two seconds during the timing intervals 90 to the circuit which supplies the radar signal, and for the next two seconds duringfthe timing intervals 91 connect the storage tube apparatus to the circuit which supplies the tactical symbot signal, as shown by graph Y, Fig. 2B. Graphs X, Y and Z are all drawn to the same time scale. It will'be understood that the radar and tactical signals -may each comprise two beam positioning components for positioning the beam in two mutually perpendicular planes or directions, only one signal being shown in Fig. 2B for ease of illustration. During the time interval that the storage tube apparatus is connected to the radar signal circuit, the one-tenth second radar signal occurs, and sufcient radar indication storage is provided during the time that the radar signal is applied, to provide for a radar indication which lasts substantially four seconds, it being recalled that erase pulses are continually applied to the storage mesh support during the four seconds. Thereafter, during the two second period that the storage tube apparatus is connected to receive the tacticaly symbol signal, this signal occurs, lasting one second during which the tactical symbol 89 moves across the screen of the storage tube for example, from left to right as seien in Fig. 2A. The positive gate proportional to the rate of movement of the writing beam is adjusted at 79 to provide for considerably less storage, since the tactical symbol is moving rapidly and long persistence at any one spot on the screen wouldv result in blurring. It will be recalled that the gate controlled by control 79 does not substantially affect beam intensity while the beam is stationary, so that the storage of the tacical symbol may be adjusted for proper brightness without substantially affecting the radar' indication.

Where the radar signal is always' present', the apparatus is adjusted to provide the proper amount of radar indication storage during the iirst two-second period, so that the radar indication persists with suicient brightness during the second two-second period during which the moving tactical symbol is provided.

Any suitable means, not shown, may be provided for heating the cathodes of the electron guns.

In summary, the invention employs a circuit arrangement which utilizes beam dwell time, that is, the time that the writing beam is directed at a particular spot, to control the beam intensity and therefore control the amount of secondary emission from the insulator surface and the charge thereon, to thereby control the number of flood gun electrons striking the phosphorescent surface and accordingly control the brightness of the indication on the viewing screen.

It will be readily understood that other types of direct viewing storage tubes may be used, suitable rearrangement of connections, potentials and polarities being made where required.

Whereas the invention has been shown and described with reference to a storage tube having one writing gun to which two different signals for respectively producing a relatively long enduring stationary indication and an indication of relatively short duration are alternately applied on a time-sharing basis, it should be understood that a storage tube having two writing guns could be employed, one writing gun supplying the radar information and indication, the other writing gun supplying the moving symbol indication, and that in this case, the automatic beam intensity control circuit would be applied only to the writing gun providing the moving symbol, and not to the writing gun providing the stationary indication.

Whereas the invention has been shown and described with reference to a storage tube having an electrical input and a visual output, it should be understood that other types of storage tubes could be employed. For example, the invention is applicable to apparatus employing electn'cal input-electrical output storage tubes Where it is desirable to obtain an output signal which has an amplitude more or less independent of changes in the rate of movement of the writing gun of the tube.

Whereas apparatus for moving the writing beam in two substantially mutually perpendicular planes or directions has been shown, -it `should be understood that Imovement in one plane only could be provided for, in which case the sum circuit 65, one of the iilters and one of the differentiators could be dispensed with.

In adjusting the hereinbefore described apparatus for proper operation where two indications having widely different desired persistences are to be simultaneously displayed, for example, a four second radar indication and a tactical symbol which moves across the entire viewing screen in one second, the rate of erasing from the storage dielectric is ypreferably adjusted in accordance with the time of storage of the long persistence radar indication, by varying any or all of the erase pulse generator controls 81-83 inclusive. The erase pulse may, for example, have an amplitude of to l0 volts and a width of 100 microseconds. Thereafter, the erase rate is not varied; proper erasing for the rapidly moving symbol may be provided for by adjusting beam intensity by use of any or all of controls 76, 79, and potentiometer arm 78.

It should be understood that, to the extent that the design of the storage tube used permits, circuit parameters may be adjusted to vary viewing screen persistence. Preferably, the storage tube used Will have a screen which itself has a relatively short persistence; electrically controllable long persistence is `provided by the tube storage.

If desired, lead means 50 and 55 may have isolation devices, not shown, such as cathode followers, interposed between filters S9 and `60 respectively and deflection ampliers 48 and 46 respectively, and the signal to produce the long persistence or radar indication applied directly at the deection ampliers, suitable adjustment of potentiometer arm 78 being made.

It should be understood that the invention is readily adapted for an intensity modulated symbol or indication.

Whereas the invention has been shown and described with reference to the preferred embodiment thereof which gives satisfactory results, it should be understood that modifications may be made and equivalents substituted without departing from the spirit and scope of the invention.

We claim as our invention:

l. In storage tube apparatus for simultaneously providing a first stationary indication and a second moving indication, in combination, storage tube means including a direct viewing storage tube having a writing gun, a ood gun, a viewing screen adapted to give a visual indication while electrons impinge thereon, and a storage element positioned between said screen and both said guns, signal input means adapted to have first and second signals alternately applied thereto, said first signal providing the rst indication, said rst signal being composite and including at least one direct current beam positioning component and an indication component, beam deecting means associated with said writing gun and connected to said signal input means, gate generating means operatively connected to the signal input means and to the storage tube to control the intensity of the beam of the writing gun in accordance with the amplitude of the gate, said gate generating means including means for adjusting the amplitude of the gate to a first value while said irst signal is applied to the signal input means, and means operatively connected to said storage element for erasing the storage at an adjustable rate independent of the movement of the beam, said gate amplitude and said erase rate being adjusted with respect to each other so that sufficient storage is provided by the rst signal whereby the first indication remains visible during the time that the iirst signal is not applied to the signal input means, the second signal being composite and including at least one varying direct current beam positioning component and an indication component, said second signal while applied to the beam dellecting means providing the second moving indication on the screen, said gate generating means including means to provide a variable gate which varies in amplitude as -an adjustable function of the rate of movement of the beam and of the second indication across the screen of the viewing tube, said function being adjusted to a value in accordance with the adjusted erase rate to automatically control the intensity of the writing beam and the storage in the storage element at a value such that the number of electrons from said ood gun arriving at said Viewing screen maintains the brightness of the second indication at a predetermined value as the second indication moves across the screen.

2. In storage tube apparatus for simultaneously providing a lirst stationary indication and a second moving indication, in combination, storage tube means including a direct viewing storage tube having a writing gun, a flood gun, a viewing screen adapted to give a visual indication while electrons impinge thereon, and a storage element positioned between said screen and both said guns, signal input means, erase means operatively connected to the storage element for erasing at an adjustable rate, beam detlecting means operatively connected to the signal input means and to said writing gun, said signal input means being adapted to have first and second signals alternately applied thereto, the rst signal providing the rst indication and the second signal providing the second indication, the rst signal being composite and including a direct current beam positioning component and an indication component, and beam intensity control means connected to the signal input means and to the writing gun,

said beam inensity'catrbi meansfinehdisgsrst adjusting means foradjusting the intensity oft-he beam of the Writing gun in accordance with the erase rate and the time interval between the applicationsof the'r'st'si'gnal `to the signal input means to provide-for 'sufiicint storage in the storage element to ensure; astationary first 'indication which is continuously visible, i said second signal including a varying direct current Vbeamlpositioiiing-"component and an indication component, said varying direct current component being applied to said beam intensity control means, said beam intensity control means including other means for adjusting the beam intensity whereby the intensity of the beam is automatically controlled as an adjustable function of the rate of movement of the beam and of the second indication across the viewing screen, said function being adjusted to a v-alue in accordance with the erase rate which provides sufficient storage to provide a moving second indication of selected brightness and in which blurring is substantially eliminated.

3. In storage tube apparatus for simultaneously providing a first stationary indication and a second moving indication, in combination, storage tube means including a direct viewing storage tube having a writing gun, a flood gun, a viewing screen, and a storage element positioned between the screen and both the guns, erase means operatively connected to the storage element for erasing at an adjustable rate, signal input means adapted to have first and second signals alternately applied thereto, the first signal providing the first indication and the second signal providing the second indication, beam defiecting means associated with said Writing gun and connected to said signal input means, the first and second signals being composite and each including a direct current beam positioning component and an indication component, and beam intensity control means operatively connected to the signal input means and to the writing gun, said beam intensity control means being adjustable to a first setting in accordance with the erase rate and the duration of the first signal whereby the first signal provides sufficient storage for a visible first indication which persists between reoccurrences of the first signal, said beam intensity control means including other adjusting means for automatii cally varying the beam intensity as an adjustable function of the rate of change of the direct current beam positioning component of the second signal and therefore in accordance with the rate of movement of the second indication across the viewing screen to provide a second moving indication of the desired brightness in Which blurring is substantially eliminated.

4. In storage tube apparatus for simultaneously providing a first stationary indication and a second moving indication, in combination, storage tube means including a direct viewing storage tube having a writing gun, a flood gun, a viewing screen adapted to give a visual indication while electrons impinge thereon, and a storage element positioned between said screen and both said guns, erase means operatively connected to said storage element for erasing the storage -at an adjustable rate independent of the rate of movement of the writing beam, signal input means, beam defiecting means associated with said Writing gun and operatively connected to said signal input means, said signal input means being adapted to have first and second signals alternately applied thereto, the first signal providing the first indication and the second signal providing the second indication, each of said first and second signals being composite and including a direct current beam positioning component and an indication component, gate generating means including means for generating a gate of adjustable amplitude when no control signal is applied to the gate generating means and means for varying the amplitude of the gate as an adjustable function of the amplitude of a control signal applied to the gate generating means, and differentiating means operatively connecting the gate generating means to the signal input means for supplying to the gate generating -lr'ians a fcontrol Isignal which varies' in amplitude iin acordancewith variationsin the 'rate of; changerin'a direct 'current beam positioning component, sa.d"gate:generat ing means being connected to saidstoragetube to have the gate thereof control the intensity of the beam of lthewriting gun yto `thereby control thestorage in said storage element vand-accordingly control thenumber of electrons: 'from saidfiood-gun arriving 'at said'viewing screen, the: Jgate'being adjusted to a first amplitudefin 'accordance' with the erase rate and the duration of saidfirstsignalrto' provide for sufficient storage to maintain a visible first indication between reoccurrences of the first signal, the gate being further adjusted in accordance with said function and the value of the control signal to provide the' correct amount of storage to ensure a moving second indication of the desired brightness in which blurring is substantially eliminated.

5. In storage tube apparatus for simultaneously providing a first stationary indication and a second moving indication, in combination, storage tube means including a direct viewing storage tube having a writing gun, a flood gun, a viewing screen adapted to give a visual indication while electrons impinge thereon, and a storage element positioned between said screen and both said guns, beam defiecting means associated with said writing gun, signal input means operatively connected to the Ibeam def'lecting means, said signal input means being adapted to have first and second signals alternately applied thereto, the first signal producing the first indication and the second signal producing the second indication, the first signal being composite and including at least one direct current beam positioning component and an indication component, and storage control means operatively connected to said storage tube, said storage control means including erase means operatively connected to the storage element for erasing the storage at an adjustable rate, said storage control means also -including beam intensity control means operatively connected to the signal input means, said beam intensity control means being adjustable whereby suicient storage is provided by the rst signal in accordance with the adjusted erase rate to provide `a visible first indication on Ithe Viewing screen which lasts between reoccurrences of the first signal, said second signal being composite and including at least one varying direct current beam positioning component iand an indication component, said beam intensity control means being further adjustable to provide for automatically varying the intensity of the beam as an adjustable function of the rate of movement of the beam to thereby provide storage in an amount which ensures a visible moving second indication and which is erased at said adjusted erase rate suiciently rapidly to prevent blurring and the formation of an undesired trace on the viewing screen.

6. In storage tube apparatus for simultaneously providing a first stationary indication and a second moving indication, in combination, storage tube means including a direct viewing storage tube having a writing gun for producing a writing beam, a flood gun, -a viewing screen adapted to give a visual indication while electrons impinge thereon, and a storage element positioned between said screen and both said guns, signal input means, beam positioning means, erase means operatively connected to said storage element for erasing the storage at an adjustable rate independent of the movement of the writing beam, and adjustable beam intensity control means operatively connected to the signal input means and to the storage tube, the signal input means being adapted to have first and second signals applied thereto alternately, the first signal providing for the first indication and the second signal providing for the second indication, the first and second signals being composite and each including a direct current beam positioning component and an indication component, said beam intensity control means being first adjusted in accordance with the adjusted erase rate and the duration of the rst signal to provide the correct amount of storage to maintain a constantly visible first indication, said beam intensity control means being thereafter `adjusted to automatically vary the intensity of the beam in accordance with the rate of variation in a varying direct current beam positioning component of the second signal and the adjusted erase rate to provide a second moving indication of selected brightness in which blurring is substantially eliminated.

References Cited in the le of this patent UNITED STATES PATENTS Swedlund Apr. 27, 1937 Read Mar. 16, 1943 Miller et al. Apr. 1, 1947 Pensak Sept. 10, 1957 `McKim Nov. 11, 1958 

